1. Field of the Invention
The present invention relates to an endoscope capable of undergoing autoclaving (sterilization with high-temperature high-pressure steam) when the endoscope must be disinfected or sterilized after being used.
2. Description of the Related Art
Endoscopes are widely employed in the field of medicine these days. The endoscope has an elongated insertion member inserted into a body cavity for the purpose of observing a deep region in the body cavity, or the endoscope is used in combination with a therapeutic instrument, if necessary, to perform a cure or remedy. For the medical-purpose endoscope, it is essential to reliably disinfect or sterilize a used endoscope.
Recently, autoclaving (sterilization with high-temperature high-pressure steam) is getting mainstream in sterilization of medical equipment. This is because autoclaving is no labor-intensive but low-cost, and medical equipment can be used immediately after it is autoclaved.
Typical conditions for autoclaving are stipulated in the U.S. standard ANSI/AAMI ST37-1992 recommended by the American National Standards Institute and published from the Association for the Advancement of Medical Instrumentation. The standard stipulates that, for example, a pre-vacuum sterilization process should be performed at 132° C. for 4 min and a gravity settling sterilization process should be performed at 132° C. for 10 min.
The above environmental conditions for autoclaving are quite severe for endoscopes that are precision electronic apparatuses. In order to realize an endoscope that withstands the environment to undergo autoclaving, unlike an endoscope that shall be reused after subjected to a general disinfecting or sterilizing means, various measures must be taken against high pressure, high temperature, steam, and so on.
Moreover, an existing endoscope has push-button switches such as remote control switches, which are used to control the actions of external units placed outside the endoscope, exposed on a control section thereof. For example, a push-button switch described in Japanese Unexamined Utility Model Publication No. 2-58401 consists of a switch, a pressing member, and a presser. The switch is exposed on the control section. The pressing member is a waterproof film that has elasticity and shields the switch to keep the switch watertight. The presser that presses the switch is fixed to the pressing member and opposed to the switch.
In general, however, the external pressure of an endoscope is relatively higher than the internal pressure thereof after the endoscope undergoes a pressurization step or a dry step that is one step of autoclaving (sterilization with high-temperature high-pressure steam). Due to a difference in pressure between the interior of the endoscope and the exterior thereof, force works on the endoscope from the exterior of the endoscope to the interior thereof. In the endoscope described in the Japanese Unexamined Utility Model Publication No. 2-58401, the soft pressing member elastically deforms toward the interior of the endoscope. An end of the presser fixed to the pressing member approaches the switch. In some cases, the end of the presser may press the switch.
Moreover, if the end of the presser presses the switch to a great extent, a very small stem that forms the switch may deform permanently. In particular, at the pressurization step, not only a load derived pressure but also a thermal load derived from high temperature may be imposed on the switch. In some cases, therefore, the switch itself may deform.
Furthermore, after the dry step is completed, if the endoscope is left as it is for a prolonged period of time, force works on the endoscope from the exterior of the endoscope to the interior thereof for the prolonged period of time. Consequently, the stem may be deformed permanently. Eventually, when a user presses the push-button switch, the user may have a different sense of touch.
Moreover, an existing endoscope has elongated resin tubes incorporated in an insertion member thereof. The tubes are used as an aeration/perfusion channel, a therapeutic instrument passage channel, and others. When the endoscope is autoclaved, since the interior of the endoscope is sealed, if the resin tubes expand to increase their outer diameters due to pressure applied at the pressurization step, the other built-in components of the endoscope may be pressured. If one of the built-in components, for example, a light guide is pressured, such accident may happen that a fiber bundle over which illumination light is propagated is broken in the middle thereof.
There is a demand for an endoscope in which even if resin tubes expand at a pressurization step of autoclaving, the resin tubes do not pressure the other built-in components after completion of the autoclaving. Also demanded is an endoscope in which even if a flexible tube contracts to decrease its inner diameter due to pressure applied at a pressurization step, at least after the autoclaving is completed, resin tubes do not pressure the other built-in components. Also demanded is an endoscope in which resin tubes will not pressure the other built-in components even at the pressurization step.
Moreover, an existing endoscope has, for example, a soft breakage-of-insertion member preventing member engaged with the periphery of a flexible tube, which serves as part of the surface of a housing of the endoscope, in order to keep the flexible tube fluid-tight. In an atmospheric-pressure environment, fluid will not invade into the interior of the endoscope through the junction between the breakage-of-insertion member preventing member and flexible tube. When the endoscope is autoclaved, steam invades into the junction between the breakage-of-insertion member preventing member and flexible tube, and eventually into the interior of the endoscope because of pressure applied at a pressurization step.
At a dry step, on the other hand, the internal pressure of an autoclave is negative because of decompression. However, if the junction between the breakage-of-insertion member preventing member and flexible tube is kept fluid-tight, there is a fear that steam having invaded into the junction and the interior of the endoscope at the pressurization step may stagnate in the junction and the interior of the endoscope. In particular, if steam stagnates in the junction between the breakage-of-insertion member preventing member and flexible tube, a metallic part employed in the junction may corrode.